In containers which are formed from resilient sheet plastic material, it has been usual to form means to lock the sections which are hinged together by means of protuberances on the telescoping side walls of one section and recesses on the side wall of the other section along the walls which are distant from the hinge in order to hold the two sections in closed position. This does not lock the sections along the hinge side of the box together and because of the resiliency of the box does not form a firm connection between the sections when closed.